Voltage generating apparatus, current generating apparatus, and test apparatus

ABSTRACT

There is provided a voltage generating apparatus that outputs a power source voltage from a voltage outputting terminal. The apparatus includes a voltage outputting section that outputs the power source voltage according to a current or voltage to be input, a first differential amplification section that compares the power source voltage and a preset first reference voltage to output a first control current or voltage reducing the power source voltage output from the voltage outputting section when the power source voltage is larger than the first reference voltage and output the first control current or voltage raising the power source voltage output from the voltage outputting section when the power source voltage is smaller than the first reference voltage, a current detector that detects a detecting voltage according to a power source current output from the voltage outputting terminal, a second differential amplification section that compares the detecting voltage detected from the current detector and a second reference voltage to output a second control current or voltage reducing the power source voltage when a value obtained by subtracting the second reference voltage from the detecting voltage is larger, an addition section that inputs a current or voltage obtained by adding the first control current or voltage and the second control current or voltage into the voltage outputting section, and a third differential amplification section that supplies a voltage obtained by amplifying a difference voltage obtained by subtracting the detecting voltage from a preset third reference voltage to the second differential amplification section as the second reference voltage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a voltage generating apparatus, acurrent generating apparatus, and a test apparatus. More particularly,the present invention relates to a voltage generating apparatus foroutputting a power source voltage, a current generating apparatus foroutputting a power source current, and a test apparatus for testing adevice under test.

2. Related Art

FIG. 7 is a view showing relation of a power source voltage V_(O) to apower source current I_(O) in a voltage generating apparatus including aconventional current limiting circuit. Conventionally, there has beenknown a voltage generating apparatus including a current limitingcircuit that limits an electric current so that the electric currentexceeding a predetermined value does not flow into a load. The limitingcircuit detects a power source current I_(O), and descends a powersource voltage V_(O) to constant gain when the detected power sourcecurrent I_(O) exceeds a limiting current I_(CLP).

Meanwhile, in a conventional voltage generating apparatus, a differencebetween a limiting current I_(CLP) at the limit start and a power sourcecurrent I_(SHORT) at the load short (a power source voltage V_(O)=0) islarge. When the power source current I_(SHORT) at the load short islarge, a conventional voltage generating apparatus may flow a largecurrent into a load to destroy the load. Therefore, it is desirable thata difference between a limiting current I_(CLP) at the limit start and apower source current I_(SHORT) at the load short is small in a voltagegenerating apparatus.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a voltagegenerating apparatus, a current generating apparatus, and a testapparatus that can solve the foregoing problems. The above and otherobjects can be achieved by combinations described in the independentclaims. The dependent claims define further advantageous and exemplarycombinations of the present invention.

That is, according to the first aspect of the present invention, thereis provided a voltage generating apparatus that outputs a power sourcevoltage from a voltage outputting terminal. The voltage generatingapparatus includes: a voltage outputting section that outputs the powersource voltage according to a current or voltage to be input; a firstdifferential amplification section that compares the power sourcevoltage and a preset first reference voltage to output a first controlcurrent or voltage reducing the power source voltage output from thevoltage outputting section when the power source voltage is larger thanthe first reference voltage and output the first control current orvoltage raising the power source voltage output from the voltageoutputting section when the power source voltage is smaller than thefirst reference voltage; a current detector that detects a detectingvoltage according to a power source current output from the voltageoutputting terminal; a second differential amplification section thatcompares the detecting voltage detected from the current detector and asecond reference voltage to output a second control current or voltagereducing the power source voltage when a value obtained by subtractingthe second reference voltage from the detecting voltage is larger; anaddition section that inputs a current or voltage obtained by adding thefirst control current or voltage and the second control current orvoltage into the voltage outputting section; and a third differentialamplification section that supplies a voltage obtained by amplifying adifference voltage obtained by subtracting the detecting voltage from apreset third reference voltage to the second differential amplificationsection as the second reference voltage.

The current detector may include: a series resistor that is provided onelectric wiring between an output of the voltage outputting section andthe voltage outputting terminal; and a differential amplifier thatdetects the power source current by outputting a detecting voltageaccording to a potential difference between both ends of the seriesresistor.

According to the second aspect of the present invention, there isprovided a current generating apparatus that outputs a power sourcecurrent from a current outputting terminal. The current generatingapparatus includes: a current outputting section that outputs the powersource current according to a current or voltage to be input; a currentdetector that detects a detecting voltage according to the power sourcecurrent output from the current outputting terminal; a fourthdifferential amplification section that compares the detecting voltageand a fourth reference voltage according to a preset first referencecurrent to output a first control current or voltage reducing the powersource current output from the current outputting section when the powersource current is larger than the first reference current and output thefirst control current or voltage raising the power source current outputfrom the current outputting section when the power source current issmaller than the first reference current; a fifth differentialamplification section that compares a power source voltage at thecurrent outputting terminal and a fifth reference voltage to output asecond control current or voltage reducing the power source current whena value obtained by subtracting the fifth reference voltage from thepower source voltage is larger; an addition section that inputs acurrent or voltage obtained by adding the first control current orvoltage and the second control current or voltage into the currentoutputting section; and a sixth differential amplification section thatsupplies a voltage obtained by amplifying a difference voltage obtainedby subtracting the power source voltage from a preset sixth referencevoltage to the fifth differential amplification section as the fifthreference voltage.

The current detector may include: a series resistor that is provided onelectric wiring between an output of the current outputting section andthe current outputting terminal; and a differential amplifier thatdetects the power source current by outputting a detecting voltageaccording to a potential difference between both ends of the seriesresistor.

According to the third aspect of the present invention, there isprovided a test apparatus that tests a device under test. The testapparatus includes: a voltage generating apparatus that outputs a powersource voltage to be supplied to the device under test from a voltageoutputting terminal; and a test processing section that tests the deviceunder test in a state that the voltage generating apparatus has suppliedthe power source voltage to the device under test, in which the voltagegenerating apparatus includes: a voltage outputting section that outputsthe power source voltage according to a current or voltage to be input;a first differential amplification section that compares the powersource voltage and a preset first reference voltage to output a firstcontrol current or voltage reducing the power source voltage output fromthe voltage outputting section when the power source voltage is largerthan the first reference voltage and output the first control current orvoltage raising the power source voltage output from the voltageoutputting section when the power source voltage is smaller than thefirst reference voltage; a current detector that detects a detectingvoltage according to a power source current output from the voltageoutputting terminal; a second differential amplification section thatcompares the detecting voltage detected from the current detector and asecond reference voltage to output a second control current or voltagereducing the power source voltage when a value obtained by subtractingthe second reference voltage from the detecting voltage is larger; anaddition section that inputs a current or voltage obtained by adding thefirst control current or voltage and the second control current orvoltage into the voltage outputting section; and a third differentialamplification section that supplies a voltage obtained by amplifying adifference voltage obtained by subtracting the detecting voltage from apreset third reference voltage to the second differential amplificationsection as the second reference voltage.

According to the fourth aspect of the present inventions there isprovided a test apparatus that tests a device under test. The testapparatus includes: a current generating apparatus that outputs a powersource current to be supplied to the device under test from a currentoutputting terminal; and a test processing section that tests the deviceunder test in a state that the current generating apparatus has suppliedthe power source current to the device under test, in which the currentgenerating apparatus includes: a current outputting section that outputsthe power source current according to a current or voltage to be input;a current detector that detects the power source current output from thecurrent outputting terminal; a fourth differential amplification sectionthat compares the power source current and a preset first referencecurrent to output a first control current or voltage reducing the powersource current output from the current outputting section when the powersource current is larger than the first reference current and output thefirst control current or voltage raising the power source current outputfrom the current outputting section when the power source current issmaller than the first reference current; a fifth differentialamplification section that compares a power source voltage at thecurrent outputting terminal and a second reference voltage to output asecond control current or voltage reducing the power source current whena value obtained by subtracting the second reference voltage from thepower source voltage is larger; an addition section that inputs acurrent or voltage obtained by adding the first control current orvoltage and the second control current or voltage into the currentoutputting section; and a sixth differential amplification section thatsupplies a voltage obtained by amplifying a difference voltage obtainedby subtracting the power source voltage from a preset third referencevoltage to the fifth differential amplification section as the secondreference voltage.

The summary of the invention does not necessarily describe all necessaryfeatures of the present invention. The present invention may also be asub-combination of the features described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a configuration of a test apparatus accordingto an embodiment of the present invention along with a device undertest.

FIG. 2 is a view showing a configuration of a voltage generatingapparatus according to an embodiment of the present invention along witha device under test.

FIG. 3 is a view showing relation of a power source voltage V_(O) to apower source current I_(O) in a voltage generating apparatus accordingto an embodiment of the present invention.

FIG. 4 is a view showing a configuration of a current generatingapparatus according to the first alternative example of the presentembodiment along with a device under test.

FIG. 5 is a view showing relation of a power source current I_(O) to apower source voltage V_(O) in a current generating apparatus accordingto the first alternative example.

FIG. 6 is a view showing a configuration of a voltage generatingapparatus according to the second alternative example of the presentembodiment along with a device under test.

FIG. 7 is a view showing relation of a power source voltage V_(O) to apower source current I_(O) in a voltage generating apparatus including aconventional current limiting circuit.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described based on the preferred embodiments,which do not intend to limit the scope of the present invention, butexemplify the invention. All of the features and the combinationsthereof described in the embodiment are not necessarily essential to theinvention.

FIG. 1 is a view showing a configuration of a test apparatus 10according to an embodiment along with a device under test 100. The testapparatus 10 includes a voltage generating apparatus 20 and a testprocessing section 22, and tests the device under test 100. The voltagegenerating apparatus 20 outputs a power source voltage V_(O) to besupplied to the device under test 100 from a voltage outputting terminal30 thereof. The test processing section 22 tests the device under test100 in a state that the voltage generating apparatus 20 has supplied apower source voltage to the device under test 100. As an example, thetest processing section 22 may have a pattern generating section 24, atest signal supplying section 26, and a deciding section 28. The patterngenerating section 24 generates a test pattern for designating a patternof a test signal. The test signal supplying section 26 supplies a testsignal according to a test pattern to the device under test 100. Thedeciding section 28 decides the good or bad of the device under testusing an output signal output from the device under test 100 accordingto the supplied test signal.

FIG. 2 is a view showing a configuration of the voltage generatingapparatus 20 according to the present embodiment along with the deviceunder test 100. The voltage generating apparatus 20 has a voltageoutputting section 34, a current detector 36, a first differentialamplification section 38, a second differential amplification section40, an addition section 42, and a third differential amplificationsection 44. The voltage generating apparatus 20 outputs the power sourcevoltage V_(O) to be supplied to the device under test 100 that is a loadfrom the voltage outputting terminal 30.

The voltage outputting section 34 outputs the power source voltage V_(O)according to an input current or an input voltage to be input. Thevoltage outputting section 34 supplies the power source voltage V_(O) tothe device under test 100 via the voltage outputting terminal 30. In thepresent embodiment the voltage outputting section 34 includes asmoothing capacitor 46 and a voltage outputting circuit 48, and outputsa power source voltage V_(O) according to an input current. Thesmoothing capacitor 46 is charged with electric currents output from theaddition section 42 to generate an input voltage V_(I) according to anintegral value of electric currents output from the addition section 42between terminals thereof. The voltage outputting circuit 48 outputs apower source voltage V_(O) according to the input voltage V_(I)generated between the terminals of the smoothing capacitor 46.

The current detector 36 detects a detecting voltage V_(X) according to apower source current I_(O) output from the voltage outputting terminal30. In the present embodiment, the current detector 36 includes a seriesresistor 50 and a first voltage output differential amplifier 52. Theseries resistor 50 is provided on electric wiring between an output ofthe voltage outputting section 34 and the voltage outputting terminal30, and generates a voltage difference in proportion to the power sourcecurrent I_(O) on both ends thereof. The first voltage outputdifferential amplifier 52 outputs a detecting voltage V_(X) obtained byamplifying a potential difference between the both ends of the seriesresistor 50. The first voltage output differential amplifier 52 detectsthe power source current I_(O) by outputting the detecting voltage V_(X)according to the potential difference between the both ends of theseries resistor 50.

The first differential amplification section 38 compares the powersource voltage V_(O) and a preset first reference voltage V_(R1). Then,the first differential amplification section 38 outputs a first controlcurrent or voltage lowering the power source voltage V_(O) output fromthe voltage outputting section 34 when the power source voltage V_(O) islarger than the first reference voltage V_(R1), and outputs the firstcontrol current or voltage raising the power source voltage V_(O) outputfrom the voltage outputting section 34 when the power source voltageV_(O) is smaller than the first reference voltage V_(R1). In the presentembodiment, the first differential amplification section 38 includes afirst voltage generating section 54 and a first current outputdifferential amplifier 56. The first voltage generating section 54generates the first reference voltage V_(R1). The first current outputdifferential amplifier 56 outputs a first control current I₁ inproportion to a voltage obtained by subtracting the power source voltageV_(O) from the first reference voltage V_(R1) generated from the firstvoltage generating section 54.

The second differential amplification section 40 compares the detectingvoltage V_(X) according to the power source current I_(O) detected fromthe current detector 36 and a second reference voltage V_(R2) thatbecomes small as the power source current I_(O) becomes larger. Then,the second differential amplification section 40 outputs a secondcontrol current or voltage lowering the power source voltage V_(O) whena value obtained by subtracting the second reference voltage V_(R2) fromthe detecting voltage V_(X) according to the power source current I_(O)is larger. In the present embodiment, the second differentialamplification section 40 includes a second current output differentialamplifier 58. The second current output differential amplifier 58 inputsthe second reference voltage V_(R2) that becomes small as the powersource current I_(O) becomes larger and the detecting voltage V_(X) thatbecomes large as the power source current I_(O) becomes larger. Then,the second current output differential amplifier 58 outputs a secondcontrol current I₂ in proportion to a voltage obtained by subtractingthe detecting voltage V_(X) from the second reference voltage V_(R2).Furthermore, the second current output differential amplifier 58 setsthe second control current I₂ to zero when the detecting voltage V_(X)shows that the power source current I_(O) is less than a limitingcurrent I_(CLP).

The addition section 42 supplies a current or voltage obtained by addingthe first control current or voltage output from the first differentialamplification section 38 and the second control current or voltageoutput from the second differential amplification section 40 to thevoltage outputting section 34 as an input current or an input voltageV₁. In the present embodiment, the addition section 42 includes acurrent adder 60. The current adder 60 outputs an electric currentobtained by adding the first control current I₁ output from the firstcurrent output differential amplifier 56 and the second control currentI₂ output from the second current output differential amplifier 58. Asan example, the current adder 60 may be a connecting point forconnecting an output port of the first current output differentialamplifier 56, an output port of the second current output differentialamplifier 58, and an input port of the voltage outputting section 34. Inthis way, the current adder 60 can charge the smoothing capacitor 46with electric currents obtained by adding the first control current I₁and the second control current I₂. Therefore, the current adder 60 caninput the input voltage V₁ according to an integral value of theelectric currents into the voltage outputting circuit 48.

The third differential amplification section 44 supplies a voltageobtained by amplifying a difference voltage obtained by subtracting thedetecting voltage V_(X) according to the power source current I_(O) froma preset third reference voltage V_(R3) to the second differentialamplification section 40 as the second reference voltage V_(R2). In thisway, the third differential amplification section 44 can output thesecond reference voltage V_(R2) that becomes small as the power sourcecurrent I_(O) becomes larger.

In the present embodiment, the third differential amplification section44 includes a second voltage generating section 62, a first resistor 64,a second resistor 66, and a second voltage output differential amplifier68. The second voltage generating section 62 generates the thirdreference voltage V_(R3). The first resistor 64 and the second resistor66 subtract the third reference voltage V_(R3) generated from the secondvoltage generating section 62 from the detecting voltage V_(X) outputfrom the first voltage output differential amplifier 52, in order togenerate a partial-pressure voltage ((V_(X)−V_(R3))/2) obtained bydividing the subtracted result by a predetermined resistance ratio (forexample, 1/2). The second voltage output differential amplifier 68supplies the second reference voltage V_(R2) in proportion to a voltageobtained by subtracting the partial-pressure voltage ((V_(X)−V_(R3))/2)generated by the first resistor 64 and the second resistor 66 from aground voltage (0V) to the second current output differential amplifier58. In this way, the second voltage output differential amplifier 68 canoutput the second reference voltage V_(R2) that becomes small as thepower source current I_(O) becomes larger.

FIG. 3 is a view showing relation of the power source voltage V_(O) tothe power source current I_(O) in the voltage generating apparatus 20according to the present embodiment. In addition, a thick dotted line inFIG. 3 shows the power source voltage V_(O) to the power source currentI_(O) when it is assumed that there is not the third differentialamplification section 44.

The first current output differential amplifier 56 increases ordecreases the first control current I₁ to be output so as to control thepower source voltage V_(O) to a predetermined value. When the powersource current I_(O) is less than or equal to the limiting currentI_(CLP), the second current output differential amplifier 58 sets thesecond control current I₂ to zero. In this way, according to the voltagegenerating apparatus 20, when the power source current I_(O) is lessthan or equal to the limiting current I_(CLP), it is possible to stablyoutput a predetermined power source voltage V_(O) by the control by thefirst current output differential amplifier 56.

Then, when the power source current I_(O) exceeds the limiting currentI_(CLP), the second current output differential amplifier 58 suppliesthe minus second control current I₂, an absolute value of which becomeslarge as the power source current I_(O) becomes large, to the currentadder 60. In other words, the second current output differentialamplifier 58 absorbs an amount of the current that becomes large as thepower source current I_(O) becomes large from the current adder 60. As aresult, the second current output differential amplifier 58 absorbs,from the current adder 60, an electric current for an amount of thefirst control current I₁ output from the first current outputdifferential amplifier 56, and additionally absorbs electric chargescharged in the smoothing capacitor 46. Therefore, the second currentoutput differential amplifier 58 reduces the input voltage V_(I) for thevoltage outputting circuit 48.

In this way, the voltage generating apparatus 20 can reduce the powersource voltage V_(O) when the power source current I_(O) exceeds thelimiting current I_(CLP), in order to control an excess current not toflow into the device under test 100.

Furthermore, the second current output differential amplifier 58 outputsthe second control current I₂ with an amount of the current according tothe difference between the second reference voltage V_(R2) that becomessmall as the power source current I_(O) becomes larger by the control ofthe third differential amplification section 44 and the detectingvoltage V_(X) according to the power source current I_(O). In is way, asshown with a solid line in FIG. 3, the voltage generating apparatus 20can reduce the power source voltage V_(O) as the power source currentI_(O) becomes large with higher DC precision in a range in which thepower source current I_(O) exceeds the limiting current I_(CLP).Therefore, the voltage generating apparatus 20 can reduce the differencebetween the limiting current I_(CLP) at the limit start and a powersource current I_(SHORT) at short of the voltage outputting terminal 30,in order to limit the power source current I_(O) with a goodcharacteristic.

In addition, as an example, the third differential amplification section44 for outputting the second reference voltage V_(R2) reduces anamplification degree in a high-frequency area (for example, anamplification degree is one), and increases an amplification degree in alow-frequency area (for example, A₂ (A₂ is a value higher than one)). Inother words, the third differential amplification section 44 may reducean amplification degree in frequency higher than fluctuation frequencyof the power source current I_(O) according to the fluctuation of a load(for example, one), and increases an amplification degree in frequencyless than or equal to fluctuation frequency of the power source currentI_(O) according to the fluctuation of a load (for example, A₂). In thisway, since the voltage generating apparatus 20 can reduce loop gain tolimit the power source current I_(O) in a high-frequency area, it ispossible to stably reduce the power source current I_(O).

FIG. 4 is a view showing a configuration of a current generatingapparatus 70 according to the first alternative example of the presentembodiment along with the device under test 100. In addition, since thecurrent generating apparatus 70 shown in FIG. 4 has the generally sameconfiguration and function as those of the voltage generating apparatus20 shown in FIG. 2, their descriptions will be omitted except points ofdifference about the generally same components as those included in thevoltage generating apparatus 20.

The test apparatus 10 may include the current generating apparatus 70that outputs a power source current I_(O) to be supplied to the deviceunder test 100 from a current outputting terminal 80, in place of thevoltage generating apparatus 20. The current generating apparatus 70 hasa current detector 36, an addition section 42, a current outputtingsection 82, a fourth differential amplification section 84, a fifthdifferential amplification section 86, and a sixth differentialamplification section 88. The current detector 36 detects the powersource current I_(O) output from the current outputting terminal 80. Inthe present alternative example, the current detector 36 includes aseries resistor 50 and a first voltage output differential amplifier 52.The series resistor 50 is provided on electric wiring between thecurrent outputting section 82 and the current outputting terminal 80.

The current outputting section 82 outputs the power source current I_(O)according to an input current or input voltage to be input. The currentoutputting section 82 supplies the power source current I_(O) to thedevice under test 100 via the current outputting terminal 80. In thepresent alternative example, the current outputting section 82 includesa smoothing capacitor 46 and a current outputting circuit 90. Thecurrent outputting circuit 90 outputs the power source current I_(O)according to an input voltage V₁ generated on the smoothing capacitor46.

The fourth differential amplification section 84 compares a detectingvoltage V_(X) according to the power source current I_(O) and a presetfourth reference voltage V_(R4). Then, the fourth differentialamplification section 84 outputs a first control current or voltagereducing the power source current I_(O) output from the currentoutputting section 82 when the power source current I_(O) is larger thanthe fourth reference voltage V_(R4), and outputs the first controlcurrent or voltage raising the power source current I_(O) output fromthe current outputting section 82 when the power source current I_(O) issmaller than the fourth reference voltage V_(R4). In the presentalternative example, the fourth differential amplification section 84includes a first voltage generating section 54 and a first currentoutput differential amplifier 56. The first current output differentialamplifier 56 outputs a first control current I₁ in proportion to avoltage obtained by subtracting a detecting voltage V_(X) detected fromthe current detector 36 from the fourth reference voltage V_(R4)generated from the first voltage generating section 54.

The fifth differential amplification section 86 compares the powersource voltage V_(O) of the current outputting terminal 80 and a fifthreference voltage V_(R5) that becomes small as the power source voltageV_(O) becomes larger. Then, the fifth differential amplification section86 outputs a second control current or voltage preferably reducing thepower source current I_(O) when a value obtained by subtracting thefifth reference voltage V_(R5) from the power source voltage V_(O) islarger. In the present alternative example, the fifth differentialamplification section 86 includes a second current output differentialamplifier 58. The second current output differential amplifier 58 inputsthe fifth reference voltage V_(R5) and the power source voltage V_(O).Then, the second current output differential amplifier 58 outputs asecond control current I₂ in proportion to a voltage obtained bysubtracting the power source voltage V_(O) from the fifth referencevoltage V_(R5). Furthermore, the second current output differentialamplifier 58 sets the second control current I₂ to zero when the powersource voltage V_(O) is less than or equal to a limiting voltageV_(CLP).

The sixth differential amplification section 88 supplies a voltageobtained by amplifying a difference voltage obtained by subtracting thepower source voltage V_(O) from a preset sixth reference voltage V_(R6)to the fifth differential amplification section 86 as the fifthreference voltage V_(R5). In this way, the sixth differentialamplification section 88 can supply the fifth reference voltage V_(R5)that becomes small as the power source voltage V_(O) becomes larger.

In the present alternative example, the sixth differential amplificationsection 88 includes a second voltage generating section 62, a firstresistor 64, a second resistor 66, and a second voltage outputdifferential amplifier 68. The first resistor 64 and the second resistor66 subtract the sixth reference voltage V_(R6) generated from the secondvoltage generating section 62 from the output voltage V_(O), in order togenerate a partial-pressure voltage ((V_(O)−V_(R3))/2) obtained bydividing the subtracted result by a predetermined resistance ratio (forexample, 1/2). The second voltage output differential amplifier 68supplies the fifth reference voltage V_(R5) in proportion to a voltageobtained by subtracting the partial-pressure voltage ((V_(O)−V_(R3))/2)generated by the first resistor 64 and the second resistor 66 from aground voltage (0V) to the second current output differential amplifier58. In this way, the second voltage output differential amplifier 68 cansupply the fifth reference voltage V_(R5) that becomes small as thepower source voltage V_(O) becomes larger, to the second current outputdifferential amplifier 58.

FIG. 5 is a view showing relation of a power source current I_(O) to apower source voltage V_(O) in the current generating apparatus 70according to the present embodiment. In addition, a thick dotted line inFIG. 5 shows the power source current I_(O) to the power source voltageV_(O) when it is assumed that there is not the sixth differentialamplification section 88.

The first current output differential amplifier 56 increases ordecreases the first control current I₁ to be output so as to control thepower source current I_(O) to a predetermined value. When the powersource voltage V_(O) is less than or equal to the limiting voltageV_(CLP), the second current output differential amplifier 58 sets thesecond control current I₂ to zero. In this way, according to the currentgenerating apparatus 70, when the power source voltage V_(O) is lessthan or equal to the limiting voltage V_(CLP), it is possible to stablyoutput a predetermined power source current I_(O) by the control by thefirst current output differential amplifier 56.

Then, when the power source voltage V_(O) exceeds the limiting voltageV_(CLP), the second current output differential amplifier 58 suppliesthe minus second control current I₂, an absolute value of which becomeslarge as the power source voltage V_(O) becomes large, to the currentadder 60. In other words, the second current output differentialamplifier 58 absorbs an amount of the current that becomes large as thepower source voltage V_(O) becomes large from the current adder 60. As aresult, the second current output differential amplifier 58 absorbs,from the current adder 60, an electric current for an amount of thefirst control current I₁ output from the first current outputdifferential amplifier 56, and additionally absorbs electric chargescharged in the smoothing capacitor 46. Therefore, the second currentoutput differential amplifier 58 reduces the input voltage V₁ for thecurrent outputting circuit 82.

In this way, the current generating apparatus 70 can reduce the powersource current I_(O) when the power source voltage V_(O) exceeds thelimiting voltage V_(CLP), in order to control an excess voltage not toflow into the device under test 100.

Furthermore, the second current output differential amplifier 58 outputsthe second control current I₂ with an amount of the current according tothe difference between the fifth reference voltage V_(R5) that becomessmall as the power source voltage V_(O) becomes larger by the control ofthe sixth differential amplification section 88 and the detectingvoltage V_(X) according to the power source voltage V_(O). In this way,as shown with a solid line in FIG. 5, the current generating apparatus70 can reduce the power source current I_(O) as the power source voltageV_(O) becomes large with higher DC precision in a range in which thepower source voltage V_(O) exceeds the limiting voltage V_(CLP).Therefore, the current generating apparatus 70 can reduce the differencebetween the limiting voltage V_(CLP) at the limit start and a powersource voltage V_(OPEN) at open of the voltage outputting terminal 30,in order to limit the power source voltage V_(O) with a goodcharacteristic.

In addition, as an example, the sixth differential amplification section88 for outputting the fifth reference voltage V_(R5) reduces anamplification degree in a high-frequency area (for example, anamplification degree is one), and increases an amplification degree in alow-frequency area (for example, A₂ (A₂ is a value higher than one)). Inother words, the sixth differential amplification section 88 may reducean amplification degree in frequency higher than fluctuation frequencyof the power source voltage V_(O) according to the fluctuation of a load(for example, one), and increases an amplification degree in frequencyless than or equal to fluctuation frequency of the power source voltageV_(O) according to the fluctuation of a load (for example, A₂). In thisway, since the current generating apparatus 70 can reduce loop gain tolimit the power source voltage V_(O) in a high-frequency area, it ispossible to stably reduce the power source voltage V_(O).

FIG. 6 is a view showing a configuration of a voltage generatingapparatus 20 according to the second alternative example of the presentembodiment along with the device under test 100. In addition, since thevoltage generating apparatus 20 shown in FIG. 6 has the generally sameconfiguration and function as those of the voltage generating apparatus20 shown in FIG. 2, their descriptions will be omitted except points ofdifference about the generally same components as those included in thevoltage generating apparatus 20 shown in FIG. 2.

A second differential amplification section 40 according to the presentalternative example has a third current output differential amplifier110, a fourth current output differential amplifier 112, and a seventhdifferential amplification section 114.

The third current output differential amplifier 110 inputs a secondreference voltage V_(R2) that becomes small as a power source currentI_(O) becomes larger and a detecting voltage V_(X) that becomes large asthe power source current I_(O) becomes larger. Then, the third currentoutput differential amplifier 110 outputs a plus current I₂₋₁ inproportion to a voltage obtained by subtracting the detecting voltageV_(X) from the second reference voltage V_(R2). Furthermore, the thirdcurrent output differential amplifier 110 sets the current I₂₋₁ to zerowhen the detecting voltage V_(X) shows that the power source currentI_(O) is not less than a limiting current I_(CLP).

The fourth current output differential amplifier 112 inputs a seventhreference voltage V_(R7) that becomes small as the power source currentI_(O) becomes larger and the detecting voltage V_(X) that becomes largeas the power source current I_(O) becomes larger. Then, the fourthcurrent output differential amplifier 112 outputs a minus current I₂₋₂of which the size of an absolute value is proportional to a voltageobtained by subtracting the seventh reference voltage V_(R7) from thedetecting voltage V_(X). In other words, the fourth current outputdifferential amplifier 112 absorbs the current I₂₋₂. In this case, as anexample, the fourth current output differential amplifier 112 may havemutual conductance of which polarity is opposite to the third currentoutput differential amplifier 110 and an absolute value is the generallysame as each other. Furthermore, the fourth current output differentialamplifier 112 sets the current I₂₋₂ to zero when the detecting voltageV_(X) shows that the power source current I_(O) is not more than aninverse limiting current −I_(CLP).

The seventh differential amplification section 114 supplies a voltageobtained by amplifying a difference voltage obtained by subtracting thedetecting voltage V_(X) according to the power source current I_(O) froma preset eighth reference voltage V_(R8) to the fourth current outputdifferential amplifier 112 as the seventh reference voltage V_(R7). Inthis way, the seventh differential amplification section 114 can outputthe seventh reference voltage V_(R7) that becomes small as the powersource current I_(O) becomes larger.

In the present example, as an example, the seventh differentialamplification section 114 may include a third voltage generating section122, a third resistor 124, a fourth resistor 126, and a third voltageoutput differential amplifier 128. The third voltage generating section122 generates an eighth reference voltage V_(R8). The third resistor 124and the fourth resistor 126 subtract the eighth reference voltage V_(R8)generated from the third voltage generating section 122 from thedetecting voltage V_(X) output from the first voltage outputdifferential amplifier 52, in order to generate a partial-pressurevoltage ((V_(X)−V_(R8))/2) obtained by dividing the subtracted result bya predetermined resistance ratio (for example, 1/2). The third voltageoutput differential amplifier 128 supplies the seventh reference voltageV_(R7) in proportion to a voltage obtained by subtracting thepartial-pressure voltage ((V_(X)−V_(R8))/2) generated from the thirdresistor 124 and the fourth resistor 126 from a ground voltage (0V) tothe fourth current output differential amplifier 112. As an example, thethird voltage output differential amplifier 128 may have anamplification factor generally same as that of the second voltage outputdifferential amplifier 68 included in the third differentialamplification section 44. In this way, the third voltage outputdifferential amplifier 128 can output the seventh reference voltageV_(R7) that becomes small as the power source current I_(O) becomeslarger.

According to the second differential amplification section 40 asdescribed above, since the current I₂₋₁ output from the third currentoutput differential amplifier 110 and the current I₂₋₂ absorbed by thefourth current output differential amplifier 112 are generally identicalwith each other when the power source current I_(O) is larger than theinverse limiting current −I_(CLP) and smaller than the limiting currentI_(CLP), it is possible to set the second control current I₂ to zero.

Then, according to the second differential amplification section 40,since the current I₂₋₁ output from the third current output differentialamplifier 110 becomes zero and the current I₂₋₂ absorbed by the fourthcurrent output differential amplifier 112 is not changed when the powersource current I_(O) is not less than the limiting current I_(CLP), itis possible to absorb the current I₂ (=I₂₋₂) from the addition section42.

Furthermore, according to the second differential amplification section40, since the current I₂₋₂ absorbed by the fourth current outputdifferential amplifier 112 becomes zero and the current I₂₋₁ output fromthe third current output differential amplifier 110 is not changed whenthe power source current I_(O) is not more than the inverse limitingcurrent −I_(CLP), it is possible to supply the current I₂ (=I₂₋₁) to theaddition section 42.

As described above, according to the voltage generating apparatus 20 ofthe present alternative example, it is possible to limit a plus or minuspower source current I_(O). in addition, a configuration of the seconddifferential amplification section 40 according to the present examplecan be applied to the fifth differential amplification section 86 shownin FIG. 5 by inputting a power source voltage V_(O) in place of adetecting voltage V_(X).

Although the present invention has been described by way of an exemplaryembodiment, it should be understood that those skilled in the art mightmake many changes and substitutions without departing from the spiritand the scope of the present invention. It is obvious from thedefinition of the appended claims that embodiments with suchmodifications also belong to the scope of the present invention.

As apparent from the above descriptions, according to the presentinvention, it is possible to realize a voltage generating apparatus, acurrent generating apparatus, and a test apparatus for limiting a powersource current and a power source voltage with a good characteristic.

1.-6. (canceled)
 7. A voltage generating apparatus that outputs a powersource voltage from a voltage outputting terminal comprising: a voltageoutputting section that outputs the power source voltage according to aninput current; a first differential amplification section that comparesthe power source voltage and a preset first reference voltage to outputa first control current reducing the power source voltage output fromthe voltage outputting section when the power source voltage is largerthan the first reference voltage and output the first control currentraising the power source voltage output from the voltage outputtingsection when the power source voltage is smaller than the firstreference voltage; a current detector that detects a detecting voltageaccording to a power source current output from the voltage outputtingterminal; a third current output differential amplification section thatcompares the detecting voltage detected from the current detector and asecond reference voltage to output a current proportional to a voltageobtained by subtracting the second reference voltage from the detectingvoltage; a fourth current output differential amplification section thatcompares the detecting voltage detected from the current detector and aseventh reference voltage to output a current proportional to a voltageobtained by subtracting the seventh reference voltage from the detectingvoltage and having a polarity opposite to the current output by thethird current output differential amplification section; an additionsection that inputs, into the voltage outputting section, a currentobtained by adding the first control current, the current output by thethird current output differential amplification section, and the currentoutput by the fourth current output differential amplification section;a third differential amplification section that supplies a voltageobtained by amplifying a difference voltage obtained by subtracting thedetecting voltage from a preset third reference voltage to the thirdcurrent output differential amplification section as the secondreference voltage; and a seventh differential amplification section thatsupplies a voltage obtained by amplifying a difference voltage obtainedby subtracting the detecting voltage from a preset eighth referencevoltage to the fourth current output differential amplification sectionas the seventh reference voltage.
 8. The voltage generating apparatus asclaimed in claim 7, wherein the third current output differentialamplification section outputs a current of 0 when the detecting voltageis greater than or equal to a first control voltage, and the fourthcurrent output differential amplification section outputs a current of 0when the detecting voltage is less than or equal to a second controlvoltage having a polarity opposite to the polarity of the first controlvoltage.
 9. A test apparatus that tests a device under test comprising:a voltage generating apparatus that outputs a power source voltage to besupplied to the device under test from a voltage outputting terminal;and a test processing section that tests the device under test in astate that the voltage generating apparatus has supplied the powersource voltage to the device under test, wherein the voltage generatingapparatus comprises: a voltage outputting section that outputs the powersource voltage according to an input current; a first differentialamplification section that compares the power source voltage and apreset first reference voltage to output a first control currentreducing the power source voltage output from the voltage outputtingsection when the power source voltage is larger than the first referencevoltage and output the first control current raising the power sourcevoltage output from the voltage outputting section when the power sourcevoltage is smaller than the first reference voltage; a current detectorthat detects a detecting voltage according to a power source currentoutput from the voltage outputting terminal; a third current outputdifferential amplification section that compares the detecting voltagedetected from the current detector and a second reference voltage tooutput a current proportional to a voltage obtained by subtracting thesecond reference voltage from the detecting voltage; a fourth currentoutput differential amplification section that compares the detectingvoltage detected from the current detector and a seventh referencevoltage to output a current proportional to a voltage obtained bysubtracting the seventh reference voltage from the detecting voltage andhaving a polarity opposite to the current output by the third currentoutput differential amplification section; an addition section thatinputs, into the voltage outputting section, a current obtained byadding the first control current, the current output by the thirdcurrent output differential amplification section, and the currentoutput by the fourth current output differential amplification section;a third differential amplification section that supplies a voltageobtained by amplifying a difference voltage obtained by subtracting thedetecting voltage from a preset third reference voltage to the thirdcurrent output differential amplification section as the secondreference voltage; and a seventh differential amplification section thatsupplies a voltage obtained by amplifying a difference voltage obtainedby subtracting the detecting voltage from a preset eighth referencevoltage to the fourth current output differential amplification sectionas the seventh reference voltage.